A technique for the collection of leukocytes, and particularly granulocytes, has been developed which involves passing blood through a non-woven fibrous material in which the diameters of the fibers are, in the main, less than 100 microns. See, for example, Swank U.S. Pat. Nos. 3,448,041 and 3,593,854, and Greenwalt, et al. U.S. Pat. No. 3,462,361. The filter members in each of these patents disclose means for collecting leukocytes and particularly granulocytes.
It has been found that the leukocytes may be eluted from the filter, from where they may then be collected and then administered to a patient in need of white cell therapy.
The LP-1 filter sold by Travenol Laboratories, Inc. is used to harvest and then elute leukocytes from a donor, for administration to a patient or the like.
This filter has a tubular housing with some flexibility, with the result that a certain amount of a shunting of blood can take place between the mass of filtration fibers in the filter and the housing.
Another blood filter which uses non-woven fibers is disclosed in our previous patent applications, Ser. No. 816,987, filed July 19, 1977, now U.S. Pat. No. 4,157,967, and Ser. No. 803,696, filed June 6, 1977.
A white cell donor may donate his cells by having blood from his system passed through a non-woven, fibrous white cell collection filter directly from his bloodstream, and then returning the filtered blood to his bloodstream containing the majority of the red cells, but with most of the granulocytes retained on the filter. After the donation process is complete, the filter may be washed free of red cells, and then the granulocytes may be harvested by elution from the filter.
By this invention, an improved filter for the collection of leukocytes and particularly granulocytes is disclosed. The filter of this invention provides a very low mortality of the red cells and platelets, which only have to pass through a relatively thin amount of non-woven fibrous material in their path through the device of this invention, while flowing from one veinous puncture site to another veinous puncture site of a white cell donor.
The design of the cartridge and the composition of the non-woven fiber arrangement is adapted for optimum performance in the collection and harvesting of viable leukocytes, while avoiding red cell and platelet mortality. Also, the filter of this invention is adapted for enhanced removal of healthy leukocytes from the filter surfaces, as well as having improved characteristics in the collection of the white cells. The white cells are also in better condition for not having to pass through a large, thick section of filter material, but instead are collected at areas near the surface of the high area filter of this invention, to avoid the stress that can be created by being forced through an extensive, thick filter. The filter of this invention allows a uniform flow of fluid, thereby increasing the accessability of leukocytes to all fiber surface areas.
The filter of this invention is also advantageous for sterilization purposes, since its high surface area reduces the time required to sterilize the filter with ethylene oxide gases, and then to dissipate the gases from the filter.
Also, the problems of shunting and clogging of the filter are reduced. The large surface area permits a low fluid velocity through the filter media for a maximum cell residence time, coupled with a minimal pressure differential. This increases the yield of granulocytes, for example, on a generally consistent basis, and also increases the viability of the red and other cells.